1. Field of the Invention
The present disclosure relates to a reciprocating compressor, and more particularly, to a reciprocating compressor with a gas bearing.
2. Background of the Invention
Generally, a reciprocating compressor serves to intake, compress, and discharge a refrigerant as a piston linearly reciprocates within a cylinder. The reciprocating compressor may be classified into a connection type reciprocating compressor or a vibration type reciprocating compressor according to the method employed to drive the piston.
In the connection type reciprocating compressor, the piston is connected to a rotating shaft associated with a rotation motor by a connection rod, which causes the piston to reciprocate within the cylinder, thereby compressing the refrigerant. On the other hand, in the vibration type reciprocating compressor, the piston is connected to a mover associated with a reciprocating motor, which vibrates the piston while the piston reciprocates within the cylinder, thereby compressing the refrigerant. The present invention relates to the vibration type reciprocating compressor, and the term “reciprocating compressor” will hereinafter refer to the vibration type reciprocating compressor.
To enhance the performance of a reciprocating compressor, a portion between the cylinder and the piston, being hermetically sealed, has to be properly lubricated. To this end, there has been conventionally known a reciprocating compressor which seals and lubricates a portion between the cylinder and the piston by supplying a lubricant such as oil between the cylinder and the piston and forming an oil film.
However, the supplying of the lubricant requires an oil supply apparatus, and an oil shortage may occur depending on operation conditions, thereby degrading compressor performance. Also, the compressor size needs to be increased because a space for receiving a certain amount of oil is required, and the installation direction of the compressor is limited because the entrance of the oil supply apparatus should always be kept immersed in oil.
Taking into consideration the disadvantages of the oil-lubricated type reciprocating compressor, as shown in FIG. 1, there has been conventionally known a technique of forming a gas bearing between the piston 1 and the cylinder 2 by bypassing a part of compressed gas between the piston 1 and the cylinder 2. In this technique, a plurality of gas flow paths 2a with a small diameter are formed in the cylinder 2, or a sintered porous material member (not shown) is provided on an inner circumferential surface of the cylinder 2. This technique can simplify a lubrication structure of the compressor because it requires no oil supply apparatus, unlike the oil-lubricated type for supplying oil between the piston 1 and the cylinder 2, and can maintain constant compressor performance by preventing an oil shortage depending on operating conditions. Also, this technique has the advantage that the compressor can be smaller in size and the installation direction of the compressor can be freely designed because no space for receiving oil is required in the casing of the compressor.
In the case the gas bearing is applied to the reciprocating compressor, a plate spring 3 is used for a resonating motion of the piston, as shown FIG. 2.
In the case the plate spring 3 is used, the piston (shown in FIG. 1) 1 constituting a compression portion 4 and the plate spring (shown in FIG. 2) 3 are connected by a flexible connecting bar (not shown) so that the piston 1 has forward movability within the cylinder (shown in FIG. 1) 2, or the connecting bar is divided into a plurality of parts 5a to 5c and connected by at least one (preferably two or more) links 6a and 6b. In the drawings, unexplained reference numeral 7 denotes a reciprocating motor.
In the case that the reciprocating compressor with a gas bearing uses the plate spring for a resonating motion as described above, the aforementioned flexible connecting bar has to be used to connect between members, or a plurality of connecting bars have to be connected by links, which may increase material costs and the number of assembly processes.
Moreover, displacement in the movement direction of the piston (hereinafter, ‘longitudinal displacement’) occurs a lot because of the characteristics of the plate spring, whereas displacement in a direction orthogonal to the motion direction of the piston (hereinafter, lateral displacement) rarely occurs. Thus, if the piston is arranged to move in a vertical direction, the piston may hang vertically downward when stopped, thus distorting the initial position of the piston. Taking this into account, the piston needs to be arranged so as to move in a horizontal direction, which is a limitation to the installation of a compression portion and a driving portion.